Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable

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Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable Semiquinone Radical and Electrochemical Behavior: A Potential Alternative of PEDOT:PSS Wanshan Liang, Lijia Xu, Xueqing Qiu, Sheng Sun, Linfeng Lan, Runfeng Chen, and Yuan Li ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01845 • Publication Date (Web): 24 Oct 2016 Downloaded from http://pubs.acs.org on November 1, 2016

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ACS Sustainable Chemistry & Engineering

1

Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable Semiquinone

2

Radical and Electrochemical Behavior: A Potential Alternative of PEDOT:PSS

3

Wanshan Liang,†,‡ Lijia Xu,§ Xueqing Qiu,*, †,‡ Sheng Sun,∥ Linfeng Lan,∥ Runfeng

4

Chen,*,§Yuan Li,*, †,‡

5 6 7

†

School of Chemistry and Chemical Engineering, South China University of

Technology, Wushan Road 381, Tianhe District, Guangzhou, China ‡

State Key Laboratory of Pulp and Paper Engineering, South China University of

8

Technology, Wushan Road 381, Tianhe District, Guangzhou, China

9

§

Key Laboratory for Organic Electronics and Information Displays & Institute of

10

Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for

11

Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9

12

Wenyuan Road, Nanjing 210023, China

13 14

∥

State Key Laboratory of Luminescent Materials and Devices, South China

University of Technology, Wushan Road 381, Tianhe District, Guangzhou, China

15 16

*E-mail: [email protected] (Yuan Li)

17

*E-mail: [email protected] (Xueqing Qiu)

18

*E-mail: [email protected] (Runfeng Chen)

19 20 21 22 1

ACS Paragon Plus Environment


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ABSTRACT:

24

Inspired by the p-doped PEDOT:PSS, a traditional anode modifier, we proposed to

25

prepare polydopamine:polystyrenesulfonate (PDA:PSS) via the self-polymerization of

26

dopamine in aqueous PSS initially. However, DA and its semiquinone radical were

27

dispersed by PSS to form DA:PSS successfully. Interestingly, strong electron spin

28

resonance (ESR) signal was detected in DA:PSS, suggesting the stable semiquinone

29

radical was formed. More importantly, water soluble DA:PSS exhibited stable and

30

quasi-reversible electrochemical oxidation behavior, and excellent film-formation

31

capability. Consequently, as an indium tin oxide (ITO) anode modifier, solution

32

processed DA:PSS film showed hole injection property in organic light emitting

33

diodes. Our results open a new avenue for the design of semiconductor and organic

34

electronic application inspired by the electron transfer of phenol derivatives such as

35

DA. Phenol-based organic electronic (POE) material has showed potential and it

36

should be taken into consideration in future.

37

Keywords: PEDOT:PSS, Hole transport material, organic light-emitting diode,

38

organic electronic, phenol

39 40 41 42 43 44 2


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For Table of Contents use only

45

46 47

Manuscript title: Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable

48

Semiquinone Radical and Electrochemical Behavior: A Potential Alternative of

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PEDOT:PSS

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Author: Wanshan Liang,†,‡ Lijia Xu,§ Xueqing Qiu,*, †,‡ Sheng Sun,∥ Linfeng

51

Lan,∥ Runfeng Chen,*,§ Yuan Li,*, †,‡

52 53

Synopsis: DA:PSS, a potential alternative of PEDOT:PSS, is supposed to be an

54

environmentally friendly p-type material.

55 56 57 58

INTRODUCTION

59

During the past more than 30 years, the dramatic development of organic electronic

60

(OE) devices, including organic light-emitting diodes (OLEDs),1-9 organic field effect

61

transistors (OFETs),10-14 organic photovoltaics (OPVs)15-20 has attracted worldwide

62

attention of chemists and material scientists. For all of devices above, the organic

63

charge transport materials are usually divided into p-type21-26 and n-type27-30 material,

64

as well as ambipolar transport31-33 material. It’s well known that p-typed materials 3



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65

refer to hole-transport materials (HTMs) and they play an indispensable role in

66

organic electronic devices. As acknowledged, it is challenging and important, also a

67

hot topic to develop high performance n-type semiconductors in recent 10 years.

68

Comparing with the n-type materials, numerous efforts have been focused on the

69

research of p-type ones. Indeed, there has been many excellent candidates for p-type

70

materials,

71

commercializing OLED.34-37 However, solution processable polymeric p-type material

72

is still in high demand for solution-processed organic electronic. Poly(3,4-theylene

73

dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) is one of the most

74

successful and excellent water soluble p-type materials as it has advantages including

75

tunable high conductivity, high transparency in UV-visible region, the capability of

76

smoothing the ITO morphology and so on.38-44 There are still some drawbacks

77

including poor device lifetime induced by its acidity, structural and electronic

78

inhomogeneity. Considering the weakness of PEDOT:PSS, many alternatives of

79

PEDOT have been widely explored in previous work.45-48 Some work related to

80

hydroquinone-quinone complexes on molecular electronics has been reported.49-50

81

Motivated by our curiosity on the potential of electron-rich aromatic phenolic

82

compounds to act as hole-transport materials, recently we further applied

83

phenol-based material such as lignin-based derivatives as p-type transport materials in

84

OPVs and OLEDs for the first time.51-56 In general, aromatic phenolic derivatives

85

(PDs) are well known as unstable compounds as they can be readily converted into

86

fragile phenolic radicals (PRs), thereby, the study on their potential as p-type material

especially

for

vacuum-deposited

small

4


molecules

in

on-going

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87

is rarely reported. In fact, PDs and PRs are not as vulnerable as we image based on

88

traditional viewpoint. To give a sample, catechol can be oxidized into semiquinone

89

radical intermediate or quinone under mild condition,57,58 along with electron

90

transport process.51-56,59 Generally, semiquinone radical is unstable because of its

91

relatively high thermodynamic potential.60,61 But in fact, for many biopolymers

92

related to catechol, such as lignin, melanin, humic acid and tannin, stable PRs and

93

persistent semiquinone radical were widely detected.62-64 To sum up, there are several

94

strategies to stabilize semiquinone radical, namely, (1) protection of the bulky and

95

hydrophobic tert-butyl group borne with catechol structure,65 (2) metalloprotein was

96

found

97

intramolecular/intermolecular hydrogen bonding in/between the aryloxyl radical

98

semiquinone hinders the further loss of one electron to form quinone,65 (4) some

99

heavy metals such as Zn2+ and Pb2+ are known to stabilize semiquinones via

100

formation of radical complexes,66-70 while some paramagnetic metal ions such Cu2+,

101

Mn2+, or Fe3+ are opposite, (5) tightly bounded three-dimensional micromulecular

102

network of lignin can also stabilize the semiquinone radical.71

to

have

the

capability

of

stabilizing

semiquinone

radical,61

(3)

103

Overviewing the interesting fundamental work above, we proposed melanin-like

104

polydopamine (PDA), with electron-rich blocks containing catechol hydroxyl and

105

semiquinone radical,72 might act as either an amorphous organic semiconductor or an

106

electronic-ionic hybrid conductor.73-75 PDA derivatives have been applied in batteries,

107

supercapacitors and catalyst as reported,76-80 while the report about PDA in OE

108

devices directly has not yet been found. Inspired by the traditional PEDOT:PSS,81,82 5



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intended

to

use

PDA to

replace

PEDOT.

To

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109

we

our

surprise,

with

110

tris(hydroxymethyl)-aminomethane (Tris) as catalyst and PSS as dopant, none of

111

self-polymerization occurred though self-polymerization of DA was vivacious and

112

polymerization degree was difficult to control as previous work. Fortunately, well

113

confirmed DA:PSS was obtained. The synthetic PDA had a problem in solubility in

114

water and other common solvents such as DMSO and DMF with high polarity. PSS

115

was introduced to ensure its good water solubility and solution processibility to

116

achieve excellent film formation. Moreover, it is exactly true that phenol-based

117

materials showed irreversible oxidation behavior.51-56 In contrast, PDA:PSS showed

118

stable and quasi-reversible electrochemical oxidation behavior. Consequently, as an

119

indium tin oxide (ITO) anode modifier, solution-processed DA:PSS film showed

120

enhanced performance in organic light emitting diodes. The mechanism was studied

121

and discussed in details.

122 123

EXPERIENMENT SECTION

124

Materials. 3-Hydroxytyramine hydrochloride (DA∙ HCl), with a purity of 98%,

125

from Energy Chemical Co. Ltd. (Shanghai, China), was kept in temperature of 0 ˚C.

126

Poly (styrene sulfonic acid) sodium salt (PSS, Mw equals to 70000 Da) was brought

127

from Alfa. Tris(hydroxymethyl)-aminomethane was supplied by Energy Chemical Co.

128

Ltd. (Shanghai, China) with a purity of 99.5%. All other chemicals were of analytical

129

grade, including hydrochloric acid (HCl) of 36.5%wt. The water used in laboratory

130

was deionized water. 6


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Preparation

and

Purification

of

DA:PSS.

Adjust

the

pH

of

132

tris(hydroxymethyl)-aminomethane buffer (Tris) solution to 8.5 with the addition of

133

diluted HCl. PSS (2 g, with Mw of 70 kDa) was dissolved in the buffer solution and

134

the solution was stirred for 5 min, subsequently. Finally DA∙ HCl (1 g) was fed at

135

room temperature and the reaction last for at least 12h. The DA∙ HCl monomer can be

136

partially oxidized under alkaline condition in the presence of O2 as the oxidant. With

137

the dispersion of PSS，the color of the solution changed from colorless to pale brown,

138

and finally turned to deep brown. The product was dialyzed by a dialysis membrane

139

(Special Products Laboratory, USA, MWCO of 1000 Da) to remove inorganic salt,

140

and the purified products was then freeze-dried to obtain solid power samples.

141

The pure product has a good solubility in water (> 10 mg/mL), and it also can be

142

dissolved in DMSO.

143

Oxidation of Catechol. Catechol (200 mg) was dissolved in 10 mL ethanol.

144

Catechol was oxidized easily and the color changed from colorless to brown gradually

145

in air, followed by the addition of 5 mL ammonia. After 1 h stirring at ambient

146

condition, solid oxidized catechol (OC) with a color of pale-violet-red was obtained

147

by means of evaporation.

148

UV-vis Absorption Spectra. The UV-vis absorption spectra of DA:PSS,

149

DA ∙ HCl and PSS (dialyzed by the same method as DA:PSS) aqueous

150

dispersion with a concentration of 0.1 mg/mL were measured using Shimadzu

151

UV-3600 spectrophotometer (Japan). The spectra were recorded between 190 and

152

700 nm. 7



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NMR Measurement. The 1H-NMR,

153

13

C-NMR, 1H-15N HSQC spectra were

154

recorded with DA:PSS dissolved in 0.5 mL of deuterium DMSO (DMSO6) at room

155

temperature by DRX-400 spectrometer (400 MHz 1H-NMR frequency, 600 MHz

156

13

157

Germany).

C-NMR frequency, 600 MHz 1H-15N HSQC frequency, Bruker Co., Ettlingen,

158

Electron Spin Resonance (ESR). Solid state electron spin resonance (ESR)

159

spectroscopy was used to determine the presence of free radicals of DA:PSS and OC

160

at room temperature. It was conducted by Bruker A300. Bruker (E580) frequency

161

counter was provided to calibrate the microwave frequencies. The Bruker Company

162

provides a g-factor marker of S3/2, and its g-value is supposed to be 1.9800±0.0006.

163

However no teslameter was equipped in our device, a g-factor marker at 1.9850 (see

164

Figure 4) was detected, which was 0.0050 higher than that provided by Bruker

165

Company. Therefore, the accurate g value was supposed to be the result of g value

166

(experimental data) minus 0.0050.

167

Fourier Transform Infrared Spectra (FTIR). The infrared spectra of DA:PSS and

168

DA∙HCl were recorded using Fourier transform infrared spectrometry of Auto system

169

XL/I-series/Spectrum 2000 spectrometry (Thermo Nicolet Co., Madison, WI, USA).

170

The samples were dried under vacuum and mixed with KBr. Then the mixtures were

171

tableted for infrared spectrum analysis. The spectra were recorded between 4000 and

172

500 cm-1.

173

Cyclic Voltammetry (CV). Cyclic voltammetry measurement was conducted using

174

CH760D Electrochemical Workstation, CH Instruments (Austin, Texas, USA). A 8


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175

glassy carbon electrode was first polished carefully with alumina powder and rinsed

176

with distilled water repetitively. The concentrated DA:PSS solution was deposited on

177

the surface of the clean glassy carbon electrode. The resulting electrode was immersed

178

in anhydrous dichloromethane using 0.1 M Bu4NPF6 as electrolyte. The scanning

179

potential lied between -0.2 and +1.6 V at a scan rate of 100 mV∙s-1.

180

Ultroviolet Photoelectron Spectrometer (UPS). DA:PSS solution was spin-coated

181

on TIO to get DA:PSS film. The sample was stored in a vacuum desiccator and

182

exposed only briefly to the air before introduced into an UHV chamber. UPS was

183

carried out by ESCALAB 250Xi.

184

Atomic Force Microscope (AFM). The preparation of PDA:PSS film was

185

as follow: ITO-coated glass substrates of area 2.0×1.5 cm2 were cleaned

186

ultrasonically in acetone for 15 min and then in deionized water for another 15

187

min, followed by drying in nitrogen atmosphere before use. The films of

188

DA:PSS were deposited from solution filtered through a 0.22 μm syringe filter

189

via spin-casting on the pre-cleaned ITO-coated glass substrates with rates at

190

500 rpm for 5 s and then 2000 rpm for 1 min, finally 900 rpm for 15 s. AFM

191

images of DA:PSS were observed using Park XE-100 instrument in tapping

192

mode.

193

Conductivity Test. Organic field-effect transistor (OFET) was fabricated in

194

a top-gate, bottom-contact (TG-BC) architecture with a bare Au source/drain

195

electrode and hydroxyl-free poly(per-fluorobutenylvinylether) commercially

196

known as CYTOP (400 nm) acting as the gate dielectric, which was spun-cast 9



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Page 10 of 36

197

onto the DA:PSS (20 nm). In pre-patterned electrodes, the channel width (W)

198

and length (L) are 500 and 70 μm for the device with CYTOP. Au gate

199

electrode was the deposited by thermal evaporation to complete the field-effect

200

transistors. The OFET characterizations were measured with a semiconductor

201

parameter analyzer (Agilent 4155C) and a probe station at room temperature in

202

air atmosphere.

203

Organic light-emitting devices (OLEDs). The blue OLEDs

with

204

configurations of ITO/DA:PSS/TAPC (25 nm)/mCP (8 nm)/mCP:FIrpic (10

205

wt%, 22 nm)/Tmpypb (35 nm)/LiF (1 nm)/Al (100 nm) and the control device

206

with bare ITO were fabricated, respectively. The patterned ITO glass substrates

207

were cleaned in sequential ultrasonic baths using detergent solution, deionized

208

water, acetone, alcohol and then dried at 120 oC in a vacuum oven for 20

209

minutes. After ultraviolet-ozone treating for 8 min, the DA:PSS layer was spin

210

coated on the ITO substrate and annealed using a hot plate at 120 oC for 15 min

211

to remove residual solvents. After that, the samples were transferred to a

212

thermal evaporator chamber. The TAPC (30 nm), mCP (8 nm), mCP:FIrpic (10

213

wt%, 22 nm), TmPyPb (35 nm), LiF (1 nm), and Al (100 nm) were deposited

214

subsequently by thermal evaporation under a pressure of 5×10 -4 Pa. The

215

thickness of the organic films was measured using a α-SE spectroscopic

216

ellipsometry. The active area of the device is 9 mm2. The devices without

217

encapsulation were measured immediately after fabrication in ambient

218

atmosphere at room temperature. The current-voltage-luminance characteristics 10


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219

were measured with a PR650 Spectroscan spectrometer and a Keithley 2400

220

programmable voltage-current source.

221 222

RESULTS AND DISCUSSION

223

Synthesis and Purification of DA:PSS. Initially inspired by chemical structure of

224

PEDOT:PSS, we proposed to prepare a water soluble dopant PSS dispersed PDA with

225

similar chemical doping effect reported in the work of Mostert.74 In previous reports

226

on the synthesis of PDA, the self-polymerization of DA is active under alkaline

227

condition with O2 as oxidation reagent or by means of an enzymatic oxidation as an

228

alternative approach. It is well known the synthetic PDA has a poor solubility in water,

229

even in the other common solvents such as DMSO and DMF with high polarity. In

230

order to solve this problem, PSS was added as template and dispersant under Tris

231

catalyst with pH of 8.5 at room temperature. The color of the reaction solution

232

gradually changed from colorless to pale brown, finally turning to deep brown after

233

24 hours (see Figure 1 insert). Subsequently, the product of the reaction was purified

234

by dialysis to remove catalyst Tris, free DA monomer and DA-based oligomer with

235

low molecule weight. It is interesting that DA:PSS showed a relatively lower acidity

236

with a pH of 5.3, compared with the pH of 1.9 for PEDOT:PSS.51 Considering the

237

deep brown color freeze-dried product, we proposed that DA was oxidized into new

238

compounds.

11



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239 240

Figure 1. The UV-vis spectra of 0.1mg/mL PSS, DA∙HCl and DA:PSS in H2O. The inset is

241

DA∙HCl solid, DA∙HCl in H2O, DA:PSS solid and DA:PSS in H2O, respectively (from left to

242

right).

243 244

Chemical structure analysis of DA:PSS. In order to study the chemical structure

245

and the origin of deep brown color of DA:PSS， we tested the UV-vis absorption of

246

DA:PSS, DA∙ HCl and PSS in aqueous solution. It is noteworthy that DA:PSS

247

showed obvious absorption ranged from 300 nm to 600 nm (Figure 1), which is very

248

different from those of raw material DA∙ HCl and PSS. The wide absorption spectrum

249

of DA:PSS confirmed the DA was oxidized during the preparation of DA:PSS.

250

To further illustrate the structure of our product, 1H-NMR spectra of DA:PSS and

251

DA∙ HCl were given in Figure 2. Surprisingly, the spectrum of DA:PSS was quite

252

clear, which is very different from the complex 1H-NMR spectra as previously

253

reported work on typical PDA.83,84 The broad peak signal at between 0 and 2.3 ppm

254

was ascribed to alkyl protons of PSS and the broad signal peaks at around 6.5 and

255

7.5ppm belonged to aromatic protons of PSS (Figure 2). The other signals, including

256

two kinds of methane groups and aromatic protons almost exactly overlapped with 12


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257

those of DA∙ HCl. Moreover, there were two humps at 9.0 ppm, ascribed to phenolic

258

hydroxyl protons, distinct from two sharp peaks of DA∙ HCl. The signal of amino

259

groups shifted to high field and no other signal appeared. These evidences suggested

260

no self-polymerization occurred between the DA monomers.

261 262

Figure 2. The 1HNMR spectra of (a)DA:PSS, (b) DA∙HCl and (c) OC (Catechol was oxidized in

263

the presence of alkaline ammonia in ethanol and followed by spin flash drying, OC was obtained.)

264 265

Simultaneously, two-dimensional 2D 1H-15N HSQC spectrum of DA:PSS was

266

conducted (Figure S1). There was only one intense signal at 33.0 ppm, from typical

267

nitrogen of amine. The 1H spectrum peak at 7.8ppm (associated with N) split into

268

triplet peaks. The DA intramolecular cyclization reaction did not occur based on the

269

lack of low-field indole derivatives signals.85,86 In addition,

270

DA:PSS and DA∙ HCl monomer were recorded to study whether DA monomer was

271

oxidized to dopaminequinone (Figure S2). The

13

13

C-NMR spectra of

C-NMR spectrum of DA:PSS

13



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Page 14 of 36

272

matched well with that of DA monomer, except the broad signal from PSS. More

273

importantly, no signal at around 170 ppm was observed in Figure S2 and this

274

confirmed that no dopaminequinone was generated.83,85,86 All of these evidences

275

together confirmed our proposal on the structure of DA:PSS (Scheme 1). In the

276

meanwhile, the S/N number ratio was 1.46 as shown in element analysis of DA:PSS

277

(Table 1), therefore, we supposed that there were two DA monomers arranged on

278

every three styrene sulfonic acid unit. Based on the NMR and elemental analysis data

279

collected, the structure of DA:PSS was gradually revealed and it was different from

280

that of the synthesis PDA, but has something similar with that of PEDOT:PSS (see

281

Scheme 1). Furthermore, hydrogen bonding in phenol-quinone system was mentioned

282

in many old literatures.87-89 Thus, the FTIR spectra of catechol and DA:PSS, DA∙ HCl,

283

OC and catechol were presented in Figure 3. The sharp peaks around 3352 cm-1 were

284

ascribed to the phenol groups of DA∙ HCl (Figure 3b) and catechol (Figure 3d),

285

respectively. While relatively broad peaks of DA:PSS and OC were detected in Figure

286

3a and Figure 3c, indicating that the new intermolecular hydrogen bonding was

287

produced during the oxidation of DA∙ HCl and catechol, respectively.

288

Table 1 The element analysis of DA:PSS Element

N

C

H

S

Mass ratio(%)

2.51

48.3

5.018

8.399

Calculated atom number

1

22.45

27.99

1.46

289 290 14


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291 292

Scheme 1 The structure of PEDOT:PSS, DA:PSS and typical polydopamine (PDA).

293 294

295 296

Figure 3. The FTIR spectra of (a) DA:PSS, (b) DA∙HCl, (C) OC and (d) catechol.

297 298

These interesting findings motivate us to study the underlying mechanism for the

299

unexpected result. A control experiment with catechol as starting material was

300

designed and carried out to support the results above. Catechol was oxidized in the

301

presence of ammonia, along with a color change from colorless to dark brown in

302

ethanol. Then the pale-violet-red solid product was obtained after drying and it was

303

further studied using 1H-NMR (Figure 2c). Only three types of protons, belonging to

304

three kinds of protons of catechol, were observed, however, no o-benzoquinone was 15



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305

detected. Moreover, the round stack-like signals from phenolic hydroxyl groups was

306

similar with that of DA:PSS.

307

ESR spectra of Semiquinone Radical and Mechanism. As the UV and NMR

308

results mentioned above confirmed the oxidization of DA and the color of DA:PSS

309

has turned deep brown. No quinone structure was observed. What is the origin of the

310

deep color of DA:PSS? It is usually acknowledged the color is from the quinone

311

structure. Inspired by the deep color of lignin with phenol radical,52 we further studied

312

the ESR of DA:PSS (Figure 4). An obvious g-factor marker at 1.9850 was detectable.

313

The single-line spectrum of DA:PSS is very different from the refined spectra of

314

amidogen radical.90,91 And the accurate g-factor at 2.0038 (the experimental data was

315

2.0088) was consistent with the reported g-factor of semiquinone radical.49

316 317

Figure 4. The ESR signals of solid DA:PSS and OC at room temperature.

318 319

We verified this by testing the ESR spectrum of solid OC. A single-line ESR of OC

320

with the accurate g-factor of 2.0050 (the experimental data was 2.0010) at room

321

temperature was also detected and this result was in good agreement with the result of 16


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322

DA:PSS. It was convincible that during the weak oxidation condition, semiquinone

323

radical was formed with pre-formed o-benzoquinone as an intermediate, thus no

324

o-benzoquinone proton was observed in Figure 2a and Figure 2c. As a result, we

325

proposed the synthesis, chemical structure and mechanism on semiquinone radical in

326

Scheme 2, which is similar with report on multi phenol biopolymer, such as lignin and

327

melanin.61,92 All in one word, under mild condition, DA and catechol can be oxidized

328

to form low bandgap semiquinone radical species without dopaminequinone or

329

o-benzoquinone.61

330

Scheme 2 The formation mechanism of semiquinone radical in (a) OC and (b) DA:PSS.

331 332 333

Based on all the results above, we can conclude that the self-polymerization of DA

334

was forbidden due to the electrostatic interaction between PSS and amino groups of

335

DA. The amino group involved cyclization reaction played a key role for the typical

336

self-polymerization of DA in previous work. In our work, amino group involved

337

cyclization was prevented by the addition of PSS.

338

Electrochemical Behavior of DA:PSS and OC, UPS of DA:PSS. Considering the

339

phenolic hydroxyl group and semiquinone radical in DA:PSS, cyclic voltammetry

340

(CV) was used to investigate the oxidation behavior of DA:PSS (Figure 5), and OC 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

341

was also tested for comparison. The onset potential of DA:PSS and OC was measured

342

to be 0.90V and 0.96V with respect to the Ag/AgCl reference electrode, thereby their

343

highest occupied molecular orbital energy levels (HOMO) were estimated to be -5.60

344

eV and -5.66 eV. The ultraviolet photoelectron spectroscopy (UPS) in ultrahigh

345

vacuum (UHV) was used to calibrate the HOMO level.93,94 The HOMO value of

346

DA:PSS was calculated as 5.64 eV (Figure 5b), slightly different from the result of

347

CV. It is worth noting that a quasi-reversible redox process of DA:PSS was found and

348

it had a good repeatability in 10 runs CV curves of DA:PSS in 0.1M Bu4NPF6

349

solution of dichloromethane (Figure 5a), quite different from that of electron-rich

350

phenol-based hole-transport material.51-56 And the oxidation behavior of DA:PSS in

351

0.05M H2SO4 solution was given in Figure S3. The proton provided in H2SO4 system

352

ensured the pronounced reversibility and repeatability of the CV of DA:PSS. This

353

result indicated the potential of DA:PSS as anode modifier in organic electronics.

18


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354 355

Figure 5. (a) The UPS of DA:PSS film spin-coated on ITO (left: the binding energy of secondary

356

electron cutoff

357

DA:PSS and OC film in anhydrous dichloromethane using 0.1 M Bu4NPF6 as electrolyte and it

358

was scanned for 10runs at a scan rate of 100 mV∙s-1. The HOMO level was calculated according to

359

HOMO = −(

𝑂𝑋

, right: the binding energy of Fermi level

). (b)The CV curves of

+ 4.7) eV.

360

Conductivity test of DA:PSS. OFET with DA:PSS as organic semiconductor

361

layer was used to estimate the conductivity of DA:PSS. The device architecture

362

and the output performance were shown in Figure 6. A slope of 2.48x10-11 was

363

available in the linear fitting of ID-VD curve when gate voltage (VG) equaled to

364

0V and the slope represented the reciprocal of resistance 𝑅. The conductivity

365

of DA:PSS was determined to be 1.73×10-7 S∙cm, according to the equation

366

below: 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

𝜌∙𝐿

367

𝑅=

368

к=𝜌

(2)

𝑆 1

(3)

369

where 𝜌 is the resistivity, 𝐿 is the length, 𝑆 is the cross-sectional area and к

370

is the conductivity.

371 372

Figure 6. (a) Output of an OFET with a top-gate, bottom-contact (TG-BC) architecture (W=500

373

μm, L=70 μm) measured in air atmosphere (the black one is the linear fitting). (b) The architecture

374

with DA:PSS as organic semiconductor layer based OFETs.

375 376

Performance and Morphology of DA:PSS as Anode Modifier. Based on the

377

results aforementioned and in order to evaluate the performances of DA:PSS film in

378

OLED, it was spin coated on the ITO to modify and smoothen the ITO surface. The

379

device structure was demonstrated in Figure 7. The device without anode modifier

380

was also prepared as the control device for comparison. The current density-voltage 20


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381

curve, brightness-voltage curve and detailed performance of OLED were provided in

382

Figure 7 and Table 2, respectively. DA:PSS modified anode device exhibited a higher

383

turn-on voltage (Von) of 5.1 V than the control bare ITO device and the device with

384

PEDOT:PSS as anode modifier. It is proposed that the HOMO level of DA:PSS is

385

around -5.6 eV, which is lower than the work function of ITO and PEDOT:PSS,

386

resulting in a large energy barrier for hole injection. However, the device with

387

DA:PSS modified anode showed maximum current efficiency (CEmax) of 22.5 cd/A,

388

which was obviously higher than that of the control bare ITO device, and slightly

389

lower than that of PEDOT:PSS modified device. In addition the brightness of DA:PSS

390

device is as high as 16369 cd/cm2. The operation current of DA:PSS device was

391

obviously lower than that of control device due to the modification of ITO. The power

392

efficiency of DA:PSS is even higher than that of PEDOT:PSS. The underlying

393

mechanism is that DA:PSS will reduce the roughness and smoothen the surface of

394

ITO by filling the pinhole, further decrease the leakage current, which is similar with

395

role of PEDOT:PSS and other anode modifier in organic electronics.45 However,

396

DA:PSS showed much lower conductivity comparing with that of PEDOT:PSS. We

397

will forcast that the performance of DA:PSS can be further enhanced by the

398

optimization of chemical structure, such as the introduction of lager conjugation of

399

semiquinone radical. Considering this, our result might provide a promising scaffold

400

for the design of anode modifier in future, which is supported my our previous

401

work.51-56

402

AFM was used to investigate the film-forming capability and it was demonstrated 21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

403

in Figure 8. The root mean square (RMS) of bare ITO was 3.6 nm, while DA:PSS

404

solution spin-coated ITO became much smoother and the RMS decreased as low as

405

1.1 nm. It was confirmed that DA:PSS has great potential to form uniform and smooth

406

film, which meets the requirement of anode modifier in organic electronic devices.

407 408

Figure 7. The current density-voltage, brightness-voltage curves (a), and the current efficiency

409

curves (b) of OLEDs with DA:PSS as anode modifier. (c) Device structure with DA:PSS as anode

410

modifier based OLEDs.

411 22


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412

Table 2 The photovoltaic performance of OLEDs with DA:PSS and PEDOT:PSS as anode

413

modifier and the control sample Anode modifier

Von (V)

CEmax (cd/A)

PEmax (lm/W)

None

4.5

17.5

6.32

DA:PSS

5.1

22.5

8.66

PEDOT:PSS56

4.5

25.09

8.25

414

415 416

Figure 8. The AFM morphology of (a) blank ITO, (b) DA:PSS film spin-coated on ITO with the

417

sizes of 3x3 μm.

418 419

CONCLUSION

420

Inspired by the dispersion and doping effect of PSS to PEDOT, we developed a

421

novel water soluble polymer via PSS dispersing DA and its semiquinone radical. The

422

well-known self-polymerization of DA was avoided due to the interaction of PSS with

423

amino groups of DA. This result revealed that amino group involved cyclization

424

reaction played a key role for the typical self-polymerization of DA in previous work.

425

Interestingly, DA:PSS has a stable quasi-reversible oxidation behavior, which is also

426

detected in oxidized catechol systerm. Moreover, DA:PSS, with a pH of 5.3, has 23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

427

lower acidity than PEDOT:PSS. These results indicate the potential of DA:PSS to act

428

as anode modifier. The mechanism is based on the electron transfer during the

429

oxidation of DA:PSS, owning to the structure of the phenolic hydroxyl group and

430

semiquinone radical. Our method might open a new avenue to explore the novel hole

431

transport material based on phenol-containing materials. POE materials with

432

conjugated structure has showed great potential, and it is in urgent progress and

433

should be taken into consideration in future.52,96,97

434 435

ASSOCIATED CONTENT

436

Supporting Information

437

The Supporting Information is available free of charge on the ACS Publication

438

website at DOI: **

439

Figure S1-S3 (PDF)

440 441

AUTHOR INFROMATION

442

Corresponding Authors

443

*E-mail: [email protected] (Yuan Li)

444

*E-mail: [email protected] (Xueqing Qiu)

445

*E-mail: [email protected] (Runfeng Chen)

446

Notes

447

The authors declare no competing financial interest.

448 24


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449

Acknowledgements

450

The authors would like to acknowledge the financial support of National Natural

451

Science Foundation of China (21436004, 21402054), Guangdong Province Science

452

Foundation (2014B050505006).

453 454 455 456 457 458

Reference (1) (a) Tang, C. W.; VanSlyke, S. A., Appl. Phys. Lett. Organic electroluminescent diodes. 1987, 51, 913-915. (2) Tang, C. W.; VanSlyke, S. A.; Chen, C. H., J. Appl. Phys. Electroluminescence of doped organic thin films. 1989, 65, 3610-3616.

459

(3) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.;

460

Friend, R. H.; Burns, P. L.; Holmes, A. B., Light-emitting diodes based on conjugated

461

polymers. Nature 1990, 347, 539-541.

462

(4) Coe, S.; Woo, W. K.; Bawendi, M.; Bulovic, V., Electroluminescence from

463

single monolayers of nanocrystals in molecular organic devices. Nature 2002, 420,

464

800-803.

465

(5) Muller, C. D.; Falcou, A.; Reckefuss, N.; Rojahn, M.; Wiederhirn, V.; Rudati, P.;

466

Frohne, H.; Nuyken, O.; Becker, H.; Meerholz, K., Multi-colour organic

467

light-emitting displays by solution processing. Nature 2003, 421, 829-833.

468

(6) Reineke, S.; Lindner, F.; Schwartz, G.; Seidler, N.; Walzer, K.; Lussem, B.; Leo,

469

K., White organic light-emitting diodes with fluorescent tube efficiency. Nature 2009,

470

459, 234-238.

471 472 473

(7) Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C., Highly efficient organic light-emitting diodes from delayed fluorescence. Nature 2012, 492, 234-238. (8) Li, W. J.; Pan, Y. Y.; Xiao, R.; Peng, Q. M.; Zhang, S. T.; Ma, D. G.; Li, F.; 25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

474

Shen, F. Z.; Wang, Y. H.; Yang, B., Ma, Y. G., Employing~100% Excitons in

475

OLEDs by Utilizing a Fluorescent Molecule with Hybridized Local and

476

Charg-Transfer Excited State. Adv. Funct. Mater. 2014, 24, 1609-1614.

477

(9) Peng, Q. M.; Obolda, A.; Zhang, M.; Li, F., Organic Light-Emitting Diodes

478

Using a neutral π radical as emitter: the emission from a doublet. Angew. Chem. Int.

479

Edit. 2015, 54, 7091-7095.

480

(10) Horowitz, G., Organic field-effect transistors. Adv. Mater. 1998, 10, 365-377.

481

(11) Sirringhaus, H., Device physics of solution-processed organic field-effect

482 483 484

transistors. Adv. Mater. 2005, 17, 2411-2425. (12) Zaumseil, J.; Sirringhaus, H., Electron and ambipolar transport in organic field-effect transistors. Chem. Rev. 2007, 107, 1296-1323.

485

(13) Wang, C. L.; Dong, H. L.; Hu, W. P.; Liu, Y. Q.; Zhu, D. B., Semiconducting

486

π-conjugated systems in field-effect transistors: a material odyssey of organic

487

electronics. Chem. Rev. 2011, 112, 2208-2267.

488 489 490 491 492 493

(14) Zhang, C. C.; Chen, P. L.; Hu, W. P., Organic field-effect transistor-based gas sensors. Chem. Soc. Rev. 2015, 44, 2087-2107. (15) Tang, C. W., Two-layer organic photovoltaic cell. Appl. Phys. Lett. 1986, 48, 183-185. (16) O’regan, B.; Grfitzeli, M., A low-cost, high-efficiency solar cell based on dye-sensitized. Nature 1991, 353, 737-740.

494

(17) Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J., Polymer

495

photovoltiac cells: Enhanced efficiencies via a network of internal donor-acceptor

496

heterojunctions. Science 1995, 270, 1789-1791.

497

(18) Schmidt-Mende, L.; Fechtenktter, A.; Mullen, K.; Moons, E.; Friend, R. H.;

498

MacKenzie, J. D., Self-organized discotic liquid crystals for high-efficiency organic 26


Page 26 of 36

Page 27 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

499 500 501


photovoltaics. Science 2001, 293, 1119-1122. (19) Thompson, B. C.; Frchet, J. M. J., Polymer-fullerene composite solar cells. Angew. Chem. Int. Edit. 2008, 47, 58-77.

502

(20) Congreve, D. N.; Lee, J.; Thompson, N. J.; Hontz, E.; Yost, S. R.; Reusswig, P.

503

D.; Bahlke, M. E.; Reineke, S.; Voorhis, T. V.; Baldo, M. A., External quantum

504

efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell.

505

Science 2013, 340, 334-337.

506

(21) Blochwitz, J.; Pfeiffer, M.; Fritz, T.; Leo, K., Low voltage organic light

507

emitting diodes featuring doped phthalocyanine as hole transport material. Appl. Phys.

508

Lett. 1998, 73, 729-731.

509

(22) Tress, W.; Leo, K.; Riede, M., Influence of hole-transport layers and donor

510

materials on open-circuit voltage and shape of I-V curves of organic solar cells. Adv.

511

Funct. Mater. 2011, 21, 2140-2149.

512

(23) Bi, D. Q.; Yang, L.; Boschloo, G.; Hagfeldt, A.; Johansson, E. M. J., Effect of

513

different

hole

transport

materials

on

recombination

in

CH3NH3PbI3

514

perovskite-sensitized mesoscopic solar cells. J. Phys. Chem. Lett. 2013, 4, 1532-1536.

515

(24) Jeon, N. J.; Lee, J.; Noh, J. H.; Nazeeruddin, M. K.; Gratzel, M.; Seok, S. I.,

516

Efficient inorganic-organic hybrid perovskite solar cells based on pyrene arylamine

517

derivatives as hole-transporting materials. J. Am. Chem. Soc. 2013, 135,

518

19087-19090.

519

(25) Liu, J.; Wu, Y. Z.; Qin, C. J.; Yang, X. D.; Yasuda, T.; Islam, A.; Zhang, K.;

520

Peng, W. Q.; Han, L. Y., A dopant-free hole-transporting material for efficient and

521

stable perovskite solar cells. Energy Environ. Sci. 2014, 7, 2963-2967.

522

(26) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T. B.; Duan, H. S.; Hong, Z. R.; You,

523

J. B.; Liu, Y. S.; Yang, Y., Interface engineering of highly efficient perovskite solar 27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

524

cells. Science 2014, 345, 542-546.

525

(27) Strukelj, M.; Papadimitrakopoulos, F.; Miller, T. M.; Rothberg, L. J., Design

526

and application of electron-transporting organic materials. Science 1995, 267,

527

1969-1972.

528

(28) Adachi, C.; Baldo, M. A.; Forrest, S. R.; Thompson, M. E., High-efficiency

529

organic electrophosphorescent devices with tris (2-phenylpyridine) iridium doped into

530

electron-transporting materials. Appl. Phys. Lett. 2000, 77, 904-906.

531 532

(29) Kulkarni, A. P.; Tonzola, C. J.; Babel, A.; Jenekhe, S. A., Electron transport materials for organic light-emitting diodes. Chem. Mater. 2004, 16, 4556-4573.

533

(30) Xiao, L. X.; Su, S. J.; Agata, Y., Lan, H.; Kido, J., Nearly 100% internal

534

quantum efficiency in an organic Blue-Light electrophosphorescent device using a

535

weak electron transporting material with a wide energy gap. Adv. Mater. 2009, 21,

536

1271-1274.

537

(31) Liao, Y. L.; Lin, C. Y.; Liu, Y. H.; Wong, K. T., Hung, W. Y.; Chen, W. J., An

538

unprecedented ambipolar charge transport material exhibiting balanced electron and

539

hole mobilities. Chem. Commun. 2007, 18, 1831-1833.

540 541

(32) Cornil, J.; Bredas, J. L.; Zaumseil, J.; Sirringhaus, H., Ambipolar transport in organic conjugated materials. Adv. Mater. 2007, 19, 1791-1799.

542

(33) Kulkarni, A. P.; Zhu, Y.; Babel, A.; Wu, P. T.; Jenekhe, S. A., New ambipolar

543

organic semiconductors. 2. effects of electron acceptor strength on intramolecular

544

charge transfer photophysics, highly efficient electroluminescence, and field-effect

545

charge transport of phenoxazine-based donor-acceptor materials. Chem. Mater. 2008,

546

20, 4212-4223.

547

(34) Hung, L. S.; Chen, C. H., Recent progress of molecular organic

548

electroluminescent materials and devices. Chen. Mater. Sci. Eng. R. 2002, 39, 28


Page 28 of 36

Page 29 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

549 550 551 552 553


143-222. (35) Shirota, Y.; Kageyama, H., Charge carrier transporting molecular materials and their applications in devices. Chem. Rev. 2007, 107, 953-1010. (36) So, F.; Kondakov, D., Degradation mechanisms in small-molecule and polymer organic light-emitting diodes. Adv. Mater. 2010, 22, 3762-3777.

554

(37) Xiao, L. X.; Chen, Z. J.; Qu, B.; Luo, J. X.; Kong, S., Gong, Q. H.; Kido, J.,

555

Recent progresses on materials for electrophosphorescent organic light-emitting

556

devices. Adv. Mater. 2011, 23, 926-952.

557

(38) Groenendaal, L.; Jonas, F.; Freitag, D,; Pielartzik, H.; Reynolds, J. R., Poly (3,

558

4-ethylenedioxythiophene) and its derivatives: past, present, and future. Adv. Mater.

559

2000, 12, 481-494.

560

(39) Jonsson, S. K. M.; Birgerson, J.; Crispin, X.; Greczynski, G.; Osikowicz, W.;

561

Van Der Gon, A. W. D.; Salaneck, W. R.; Fahlman, M., The effects of solvents on the

562

morphology

563

4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT-PSS) films. Synthetic

564

Met. 2003, 139, 1-10.

and

sheet

resistance

in

poly

(3,

565

(40) Kirchmeyer, S.；Reuter, K., Scientific importance, properties and growing

566

applications of poly (3, 4-ethylenedioxythiophene). J. Mater. Chem. 2005, 15,

567

2077-2088.

568

(41) Crispin, X.; Jakobsson, F. L. E.; Crispin, A.; Grim, P. C. M.; Andersson, P.;

569

Volodin, A.; Haesendonck, C. V.; Van Der Auweraer, M.; Salaneck, W. R.; Berggren,

570

M., The origin of the high conductivity of poly (3, 4-ethylenedioxythiophene)-poly

571

(styrenesulfonate) (PEDOT-PSS) plastic electrodes. Chem. Mater. 2006, 18,

572

4354-4360.

573

(42) Nardes, A. M.; Kemerink, M.; Janssen, R. A. J.; Bastiaansen, J. A. M.; Kiggen, 29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

574

N. M. M.; Langeveld, B. M. W.; Van Breemen, A. J. J. M.; de Kok, M. M.,

575

Microscopic understanding of the anisotropic conductivity of PEDOT: PSS thin films.

576

Adv. Mater. 2007, 19, 1196-1200.

577

(43) Kim, Y. H.; Sachse, C., Machala, M. L.; May, C.; Muller-Meskamp, L.; Leo, K.,

578

Highly conductive PEDOT: PSS electrode with optimized solvent and thermal

579

post-treatment for ITO-free organic solar cells. Adv. Funct. Mater. 2011, 21,

580

1076-1081.

581

(44) Alemu, D.; Wei, H. Y.; Ho, K. C.; Chu, C. W., Highly conductive PEDOT: PSS

582

electrode by simple film treatment with methanol for ITO-free polymer solar cells.

583

Energy Environ. Sci. 2012, 5, 9662-9671.

584

(45) Irwin, M. D.; Buchholz, D. B.; Hains, A. W.; Chang, R. P.; Marks, T. J., p-Type

585

semiconducting nickel oxide as an efficiency-enhancing anode interfacial layer in

586

polymer bulk-heterojunction solar cells. P. Natl. Acad. Sci. USA 2008, 105,

587

2783-2787.

588

(46) Kroon, R.; Lenes, M.; Hummelen, J. C.; Blom, P. W. M.; De Boer, B., Small

589

bandgap polymers for organic solar cells (polymer material development in the last 5

590

years). Polym. Rev. 2008, 48, 531-582.

591

(47) Li, S. S.; Tu, K. H.; Lin, C. C.; Chen, C. W.; Chhowalla, M.,

592

Solution-processable graphene oxide as an efficient hole transport layer in polymer

593

solar cells. ACS Nano, 2010, 4, 3169-3174.

594

(48) Yip, H. L.; Jen, A. K. Y., Recent advances in solution-processed interfacial

595

materials for efficient and stable polymer solar cells. Energy Environ. Sci. 2012, 5,

596

5994-6011.

597

(49) Aviram, A.; Joachim, C.; Pomerantz, M., Evidence of switching and

598

rectification by a single molecule effected with a scanning tunneling microscope. 30


Page 30 of 36

Page 31 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

599 600 601


Chem. Phys. Lett. 1988, 146, 490-495. (50) Aviram, A.; Ratner, M. A., Molecular rectifiers. Chem. Phys. Lett. 1974, 29, 277-283.

602

(51) Xia, L. P.; Xue, Y. Y.; Xiong, K.; Cai, C. S.; Peng, Z. S.; Wu, Y.; Li, Y.; Miao,

603

J. S.; Chen, D. C.; Hu, Z. H.; Wang, J. B.; Peng, X. B.; Mo, Y. Q.; Hou, L. T., Highly

604

improved efficiency of deep-blue fluorescent polymer light-emitting device based on

605

a novel hole interface modifier with 1, 3, 5-triazine core. ACS Appl. Mater. Interfaces

606

2015, 7, 26405-26413.

607

(52) Li, Y.; Hong, N. L., An efficient hole transport material based on PEDOT

608

dispersed with lignosulfonate: preparation, characterization and performance in

609

polymer solar cells. J. Mater. Chem. A 2015, 3, 21537-21544.

610

(53) Li, Y.; Zeng, W. M., PEDOT dispersed with sulfobutylated phenol

611

formaldehyde resin: a highly-efficient hole transport material in polymer solar cells.

612

Macromol. Mater. Eng. 2016, 201, 133-140.

613

(54) Li, Y.; Xue, Y. Y.; Xia, L. P.; Hou, L. T.; Qiu, X. Q., 1, 3, 5-triazine

614

crosslinked 2, 5-dibromohydroquinone as new hole-transport material in polymer

615

light-emitting diodes. Phys. Status Solidi A 2016, 213, 429-435.

616

(55) Wu, Y.; Wang, J. Y.; Qiu, X. Q.; Yang, R. Q.; Lou, H. M.; Bao, X. C.; Li, Y.,

617

Highly efficient inverted perovskite solar cells with sulfonated lignin doped PEDOT

618

as hole extract layer. ACS Appl. Mater. Interfaces 2016, 8, 12377-12383.

619

(56) Hong, N. L.; Xiao, J. Y.; Li, Y. D.; Li, Y.; Wu, Y.; Yu, W.; Qiu, X. Q.; Chen, R.

620

F.; Yip, H. L.; Huang, W.; Cao, Y., Unexpected fluorescent emission of graft

621

sulfonated-acetone-formaldehyde lignin and its application as a dopant of PEDOT for

622

high performance photovoltaic and light-emitting devices. J. Mater. Chem. C 2016, 4,

623

5297-5306. 31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 36

624

(57) Quideau, S.; Deffieux, D.; Douat Casassus, C.; Pouysegu, L., Plant polyphenols:

625

chemical properties, biological activities, and synthesis. Angew. Chem. Int. Edit. 2011,

626

50, 586-621.

627 628 629

(58) Esguerra, K. V. N.; Fall, Y.; Petitjean, L.; Lumb, J. P., Controlling the Catalytic Aerobic Oxidation of Phenols. J. Am. Chem. Soc. 2014, 136, 7662-7668. (59)

Milczarek,

G.;

Inganas,

O.,

Renewable

cathode

materials

from

630

biopolymer/conjugated polymer interpenetrating networks. Science 2012, 335,

631

1468-1471.

632 633 634 635 636 637

(60) McMillen, D. F.; Golden, D. M., Hydrocarbon bond dissociation energies. Annu. Rev. Phys. Chem. 1982, 33, 493-532. (61) Ulas, G.; Lemmin, T.; Wu, Y. B.; Gassner, G. T.; DeGrado, W. F., Designed metalloprotein stabilizes a semiquinone radical. Nat. Chem. 2016, 8, 354-359. (62) Steelink, C., Stable free radicals in lignin and lignin oxidation products. In Lignin Structure and Reaction, American Chemical Society, 1966, Vol. 5, p 51-64.

638

(63) Swan, G. A., Structure, chemistry, and biosynthesis of the melanins. In

639

Fortschritte der Chemie Organischer Naturstoffe/Progress in the Chemistry of

640

Organic Natural Products, Springer, 1974, Vol. 31, p 521-582.

641

(64) Page, S. E.; Sander, M.; Arnold, W. A.; McNeill, K., Hydroxyl radical

642

formation upon oxidation of reduced humic acids by oxygen in the dark. Environ. Sci.

643

Technol. 2012, 46, 1590-1597.

644

(65) Xi, F. D.; Barclay, L. R. C., Cooperative antioxidant effects of ascorbate and

645

thiols with di-tert-butylcatechol during inhibited peroxidation in solution and in

646

sodium dodecyl sulfate (SDS) micelles. Can. J. Chem. 1998, 76, 171-182.

647

(66) Chaudhuri, P.; Verani, C. N.; Bill, E.; Bothe, E.; Weyhermuller, T.; Wieghardt,

648

K., Electronic structure of bis (o-iminobenzosemiquinonato) metal complexes (Cu, Ni, 32


Page 33 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


649

Pd). The art of establishing physical oxidation states in transition-metal complexes

650

containing radical ligands. J. Am. Chem. Soc. 2001, 123, 2213-2223.

651

(67) Pierpont, C. G., Ligand redox activity and mixed valency in first-row

652

transition-metal

complexes

containing

tetrachlorocatecholate

653

tetrachlorosemiquinonate ligands. Inorg. Chem. 2011, 50, 9766-9772.

and

radical

654

(68) Witwicki, M.; Jerzykiewicz, M.; Jaszewski, A. R.; Jezierska, J.; Ozarowski, A.,

655

Influence of Pb (II) ions on the EPR properties of the semiquinone radicals of humic

656

acids and model compounds: High field EPR and relativistic DFT studies. J. Phys.

657

Chem. A. 2009, 113, 14115-14122.

658

(69) Christoforidis, K. C.; Un, S.; Deligiannakis, Y., Effect of metal ions on the

659

indigenous radicals of humic acids: high field electron paramagnetic resonance study.

660

Environ. Sci. Technol. 2010, 44, 7011-7016.

661

(70) Witwicki, M.; Jerzykiewicz, M.; Ozarowski, A., Understanding natural

662

semiquinone radicals-Multifrequency EPR and relativistic DFT studies of the

663

structure of Hg (II) complexes. Chemosphere 2015, 119, 479-484.

664 665

(71) Steelink, C.; Reid, T.; Tollin, G., On the nature of the free-radical moiety in lignin. J. Am. Chem. Soc. 1963, 85, 4048-4049.

666

(72) Sealy, R. C.; Hyde, J. S.; Felix, C. C.; Menon, I. A.; Prota, G., Eumelanins and

667

pheomelanins: characterization by electron spin resonance spectroscopy. Science,

668

1982, 17, 545-547.

669

(73) Bothma, J. P.; Boor, J. E.; Divakar, U.; Schwenn, P. E.; Meredith, P.,

670

Device-Quality Electrically Conducting Melanin Thin Films. Adv. Mater. 2008, 20,

671

3539-3542.

672

(74) Mostert, A. B.; Powell, B. J.; Pratt, F. L.; Hanson, G. R.; Sarna, T.; Gentle, I. R.;

673

Meredith, P., Role of semiconductivity and ion transport in the electrical conduction 33



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

674

of melanin. P. Nat. Acad. Sci. 2012, 109, 8943-8947.

675

(75) Kong, J. H.; Yee, W. A.; Yang, L. P.; Wei, Y. F.; Phua, S. L.; Ong, H. G.; Ang,

676

J. M.; Li, X.; Lu, X. H., Highly electrically conductive layered carbon derived from

677

polydopamine and its functions in SnO2-based lithium ion battery anodes. Chem.

678

Commun. 2012, 48, 10316-10318.

679

(76) Ryou, M. H.; Lee, Y. M.; Park, J. K.; Choi, J. W., Mussel-inspired

680

polydopamine-treated polyethylene separators for high-power Li-Ion batteries. Adv.

681

Mater. 2011, 23, 3066-3070.

682

(77) Liu, Y. L.; Ai, K. L.; Lu, L. H., Polydopamine and its derivative materials:

683

synthesis and promising applications in energy, environmental, and biomedical fields.

684

Chem. Rev. 2014, 114, 5057-5115.

685

(78) Zhu, J. X.; Yang, D.; Yin, Z. Y.; Yan, Q. Y.; Zhang, H., Graphene and

686

graphene-based materials for energy storage applications. Small 2014, 10, 3480-3498.

687

(79) Cai, Z. Y.; Xu, L.; Yan, M. Y.; Han, C. H.; He, L.; Hercule, K. M.; Niu, C. J.;

688

Yuan, Z. F.; Xu, W. W.; Qu, L. B., Manganese oxide/carbon yolk-shell nanorod

689

anodes for high capacity lithium batteries. Nano Lett. 2014, 15, 738-744.

690

(80) Chung, D. Y.; Jun, S. W.; Yoon, G.; Kwon, S. G.; Shin, D. Y.; Seo, P.; Yoo, J.

691

M.; Shin, H.; Chung, Y. H.; Kim, H.; Mun, B. S.; Lee, K. S.; Lee, N. S.; Yoo, S. J.;

692

Lim, D. H.; Kang, K.; Sung, Y. E.; Hyeon, T., Highly durable and active PtFe

693

nanocatalyst for electrochemical oxygen reduction reaction. J. Am. Chem. Soc. 2015,

694

137, 15478-15485.

695

(81) Pingree, L. S.; MacLeod, B. A.; Ginger, D. S., The changing face of PEDOT:

696

PSS films: substrate, bias, and processing effects on vertical charge transport†. J.

697

Phys. Chem. C 2008, 112, 7922-7927.

698

(82) Lim, F. J.; Ananthanarayanan, K.; Luther, J.; Ho, G. W., Influence of a novel 34


Page 34 of 36

Page 35 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


699

fluorosurfactant modified PEDOT: PSS hole transport layer on the performance of

700

inverted organic solar cells. J. Mater. Chem. 2012, 22, 25057-25064.

701

(83) Hong, S.; Na, Y. S.; Choi, S.; Song, I. T.; Kim, W. Y.; Lee, H., Non-covalent

702

self-assembly and covalent polymerization co-contribute to polydopamine formation.

703

Adv. Funct. Mater. 2012, 22, 4711-4717.

704

(84) Liebscher, J.; Mrowczynski, R.; Scheidt, H. A.; Filip, C.; Hadade, N. D.; Turcu,

705

R.; Bende, A.; Beck, S., Structure of polydopamine: a never-ending story? Langmuir

706

2013, 29, 10539-10548.

707 708

(85) Dreyer, D. R.; Miller, D. J.; Freeman, B. D.; Paul, D. R.; Bielawski, C. W., Elucidating the structure of poly (dopamine). Langmuir 2012, 28, 6428-6435.

709

(86) Della Vecchia, N. F.; Avolio, R.; Alfe, M.; Errico, M. E.; Napolitano, A.;

710

DIschia, M., Building-block diversity in polydopamine underpins a multifunctional

711

eumelanin-type platform tunable through a quinone control point. Adv. Funct. Mater.

712

2013, 23, 1331-1340.

713

(87) Moser, R. E.; Cassidy, H. G., Electron-transfer polymers. XXV. On

714

“hydrophobic bonding.” The effect of solvent on quinhydrone. J. Am. Chem. Soc.

715

1965, 87, 3463-3467.

716

(88) Lazarev, G. G.; Lebedev, Y. S.; Serdobov, M. V., Mechanism of the formation

717

of weak complexes of the spatially hindered quinones and phenols. Russ. Chem. Bull.

718

1978, 27, 2249-2254.

719

(89) Serdobov, M. V.; Maiorov, V. D., Complexes with hydrogen bonding between

720

sterically hindered o-quinones and pyrocatechols. Russ. Chem. Bull. 1988, 37,

721

2482-2486.

722 723

(90) Milligan, D. E.; Jacox, M. E., Matrix-Isolation Infrared Spectrum of the Free Radical NH2. J. Chem. Phys. 1965, 43, 4487-4493. 35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

724 725

(91) Ennis, C. P.; Lane, J. R.; Kjaergaard, H. G.; McKinley, A. J., Identification of the water amidogen radical complex. J. Am. Chem. Soc. 2009, 131, 1358-1359.

726

(92) Fisher, O. Z.; Larson, B. L.; Hill, P. S.; Graupner, D.; Nguyen Kim, M. T.; Kehr,

727

N. S.; De Cola, L.; Langer, R.; Anderson, D. G., Melanin-like gydrogels derived from

728

gallic macromers. Adv. Mater. 2012, 24, 3032-3036.

729

(93) Park, Y.; Choong, V.; Gao, Y.; Hsieh, B. R.; Tang, C. W., Work function of

730

indium tin oxide transparent conductor measured by photoelectron spectroscopy. Appl.

731

Phys. Lett. 1996, 68, 2699-2701.

732

(94) Zhou, Y. H.; Fuentes-Hernandez, C.; Shim, J.; Meyer, J.; Giordano, A. J.; Li, H.;

733

Winget, P.; Papadopoulos, T.; Cheun, H.; Kim, J.; Fenoll, M.; Dindar, A.; Haske, W.;

734

Najafabadi, E.; Khan, T. M.; Sojoudi, H.; Barlow, S.; Graham, S.; Bradas, J. L.;

735

Marder, S. R.; Kahn, A.; Kippelen, B., A universal method to produce low-work

736

function electrodes for organic electronics. Science 2012, 336, 327-332.

737

(95) Zeng, X. Y.; Zhang, Q. K.; Yu, R. M.; Lu, C. Z., A new transparent conductor:

738

silver nanowire film buried at the surface of a transparent polymer. Adv. Mater. 2010,

739

22, 4484-4488.

740

(96) Li, Y.; Heng, W. K.; Lee, B. S.; Aratani, N.; Zafra, J. L.; Bao, N.; Lee, R.; Sung,

741

Y. M.; Sun, Z.; Huang, K. W.; Webster, R. D.; Navarrete, J. T. L.; Kim, D.; Osuka, A.

742

Casado, J.; Ding, J.; Wu, J. S., Kinetically blocked stable heptazethrene and

743

octazethrene: Closed-shell or open-shell in the ground state? J. Am. Chem. Soc. 2012,

744

134, 14913-14922.

745

(97) Aotake, T.; Suzuki, M.; Aratani, N.; Yuasa, J.; Kuzuhara, D.; Hayashi, H.;

746

Nakano, H.; Kawai, T.; Wu, J. S.; Yamada, H., 9, 9′-Anthryl-anthroxyl radicals:

747

strategic stabilization of highly reactive phenoxyl radicals. Chem. Commun. 2015, 51,

748

6734-6737. 36


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Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable

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